The present invention relates to friction clutches, especially to friction clutches for use in motor vehicles. More particularly, the invention relates to improvements in friction clutches of the type wherein the radially outermost portion of a diaphragm spring reacts against a support, an adjacent portion of the diaphragm spring bears against a pressure plate and the inwardly extending prongs of the diaphragm spring can cooperate with a release member to relax the bias upon the pressure plate by pivoting the diaphragm spring in the region of its radially outermost portion.
It is already known to couple the prongs of the diaphragm spring to the release member and to provide an actuating device which moves the release member axially to thus disengage the clutch against the opposition of the diaphragm spring. In many instances, the coupling between the release member and the prongs of the diaphragm spring constitutes or acts not unlike a bayonet lock, i.e., it is necessary to effect an angular displacement between the diaphragm spring and the release member in order to disengage the latter from the prongs. Reference may be had to German Offenlegungsschrift No. 21 14 661 which discloses a release member with elastic fingers receivable in specially configurated slots between the prongs of the diaphragm spring. The fingers of the release member are thereupon deformed in the axial direction of the diaphragm spring with resort to a special tool and are thereby moved behind the plane of the prongs on the diaphragm spring. In the next step, the release member is rotated so that the deformed fingers engage the rear sides of the adjacent prongs.
A drawback of the just described conventional bayonet lock is that the provision of elastic fingers on the release member, the provision of a special tool for axial deformation of the fingers, and the making of specially designed slots for the fingers between certain prongs of the diaphragm spring contribute significantly to the initial cost of the friction clutch. Furthermore, the assembly of such friction clutches takes up much time and all of the operations which are necessary to couple the release member to the prongs of the diaphragm spring cannot be readily automated.
Another prior bayonet lock type coupling for use in friction clutches is disclosed in British Pat. No. 1,221,761 which proposes the use of a release member with a cylindrical extension having slots for selected prongs of the diaphragm spring. Each slot has a circumferentially extending end portion which receives a prong in response to rotation of the release member relative to the diaphragm spring.
A drawback of the patented friction clutch is that the axial length of the release member is considerable which increases the space requirements of the clutch. This is undesirable in many types of motor vehicles wherein the space which is available for installation of the clutch is often extremely small, as considered in the axial direction of the clutch. Furthermore, the assembly of the release member with the prongs of the diaphragm spring also necessitates the use of a specially designed tool which moves selected prongs of the diaphragm spring in the axial direction in order to align such selected prongs with the end portions of the respective slots prior to turning of the release member with reference to the diaphragm spring.